I am just seconding the vestibular damage:your vestibular system is what keeps you balanced. It is situated in inner ear and can be damaged with certain antibiotics, and you don't always recover from it. Symptoms are dizziness and bouncing vision when you move, difficulty balancing esp in low lighting, and nausea - again usually with motion. Try to walk on a straight line, if you battle it may be this. Also, focus on some small writing on the wall that you can read when sitting still, now move your head slowly sideways and then up and down, if you can't read it anymore it is also an indication that your vestibular system may be damaged. Sometimes you appear to be drunk (even tho you're not). I got my damage with gentamycin even tho all my levels were checked and normal, 8 yrs ago, and still have not recovered 100%. Good luck!
Just to add: when you get tired the vestibular symptoms can get a lot worse too. If your inner ear doesn't work properly, your other senses like eyes and muscles kicks in to help your body compensate for your lacking balance. But if you are tired your body battles more to do this.
